Acrylonitrile-butadiene-styrene graft copolymer resin (hereinafter, ABS resin) generally has good impact resistance, processability, mechanical strength, heat distortion temperature and gloss. Therefore, the resin has been widely used in the manufacture of electric or electronic goods, office automation (OA) instruments, and the like. However, ABS resins used in the manufacture of electronic product housings for LCDs, PDP TVs, audio equipment, and the like, tend to show scratches as a result of injection molding or during normal usage. Further, it can be difficult to impart a desired color to the ABS resin, which can decrease its commercial value.
To avoid this problem, the surface of the molded ABS resin article can be coated with urethane or UV or scratch-resistant acryl. However, these coating methods require post-processing treatment. This can complicate the manufacturing process and result in a high defect rate, which in turn can decrease productivity. Further, these coating methods can give rise to a problem of environmental contamination. Therefore there remains a need for a scratch resistant resin having improved gloss and impact resistance and which can be readily processed using injection molding processes.
Scratch resistant resins should have colorability and high gloss, because molded articles produced using such resins, unlike conventional ABS resin, typically are not coated with a urethane coating. Conventional ABS resin does not have sufficient scratch resistance even when it is coated with urethane.
Acryl resin, PMMA resin, and the like are examples of scratch resistant materials which do not require a urethane coating and which have good colorability and gloss. However, PMMA resin has poor impact resistance and insufficient moldability, which can make injection molding difficult. Therefore, this material is generally molded as an extrusion sheet and the extruded sheet is attached to a molded article. However, this method can be expensive and have a high defect rate due to post-processing steps.
Besides PMMA resin, methyl methacrylate-acrylonitrile-butadiene-styrene resin (g-MABS or so-called “transparent ABS resin”) can be used as a scratch resistant material. Although the transparent ABS resin has good colorability, gloss, and impact resistance, it does not have sufficient scratch properties such as R-hardness and flexural modulus. Accordingly, the material can warp or bend during molding processes.
Further, ABS/PMMA alloy has poor colorability and does not exhibit sufficient scratch resistance, although it has good impact resistance.